The American Cancer Society estimates that in the United States in 2013, 238,590 new cases of prostate cancer (PCa) will be diagnosed compared with approximately 99,000 cases diagnosed in 1988 attributable to the advent of prostate-specific antigen (PSA) screening. Consequently, there has been stage migration with earlier stage at diagnosis. Presently, 92% of incident PCa are locoregional versus metastatic. Hence, only 29,720 men are estimated to die from this disease in 2013. Accurate staging before treatment is desirable given the relatively high number of men who must be treated to prevent PCa-specific death. PCa has a long latency period and consequently more men die with rather than from this disease. Hence, a significant proportion of US men with localized PCa are overdiagnosed and overtreated with attendant morbidity and significant cost escalations as insignificant tumors were detected via aggressive screening procedures.
Transrectal ultrasound (TRUS) guided tissue biopsy of the prostate is the current method of screening for PCa. Pathological examination of tissue needs to confirm the presence of the disease. However, prostate biopsies are subjected to serious sampling errors and frequently miss aggressive PCa that warrant definitive therapy during initial screenings. The PCa detection rate according to the current standard of care for TRUS-guided needle biopsies with 10-12 biopsy cores is only 25-30%, while more than 50% of cancers that require definitive treatment remain undetected during initial biopsies. Such undetected cancers due to false negative biopsies are at risk of spreading beyond the prostate gland and metastasizing to distant sites. Even when PCa were diagnosed by prostate biopsies, they may fail to provide accurate information regarding histologic grade and stage of the disease that are needed for therapeutic decisions. Aggressive PCa lesions may be differentiated from non-aggressive or latent PCa based on histologic grade, pathologic stage, and volume. Aggressive PCa for organ-confined disease may be defined as those tumors with volume ≧0.5 cc or Gleason8 sum ≧7.